The biological processing of organic waste in industrial and municipal wastewater streams has long been known. Although these biological systems typically utilize microorganisms to effect biochemical decomposition of the organic waste, the processing plants may differ in the method in which the microorganisms are cultivated. In one type of system, such as an activated sludge process, the microorganisms are dispersed in an aqueous medium and decomposition effected with the microorganisms in the dispersed state while in another type, commonly referred to as a fixed film process, the microorganisms are confined and the contaminated wastewater allowed to pass in contact with the fixed film containing microorganisms.
Microorganisms, whether dispersed or carried on fixed films in sewage treatment plants, are quite vulnerable to a variety of chemicals and vulnerable to the quality of incoming sewage, in terms of chemical content. Such chemicals and sewage may drastically alter the performance characteristics of the microorganisms. In some instances where there are industrial spills, etc., the spill itself may raise the concentration of various chemical components in the sewage to a sufficient level to kill the microorganisms in the biological treatment plant, and in effect, render the plant inactive. In view of the somewhat delicate nature of microorganisms it is highly desirable to monitor the quality of incoming sewage to a plant so that appropriate action can be taken prior to introduction of the sewage to the plant. In addition, it is desirable to detect toxic substances so that appropriate action can be taken upstream of the biological treatment process to prevent the plant from shutting down. In that way one can maintain biological activity at a desired level.
A variety of test procedures have been developed for analyzing the quality of sewage for the purpose of determining the toxicity of the sewage, for determining the total chemical content in the sewage, and to determine the oxygen consumption rate of the microorganisms in that sewage. By and large many of the analytical processes have involved the utilization of complicated equipment or have taken a substantial amount of time in order to complete the test and obtain meaningful results. In many cases, because of the time required to obtain the results, sufficient time has not been provided to take appropriate action with respect to the handling of the incoming sewage. As a result, the plants in many cases were rendered inactive. Numerous patents have been issued which disclose various analytical processes for monitoring the quality of sewage. Some of these patents include:
U.S. Pat. No. 3,684,702 discloses a test procedure for determining the biochemical decomposibility of incoming sewage so as to effectively control the decomposition of the sewage under optimum conditions. The analytical technique comprises first isolating predetermined quantities of sewage, activated sludge, etc., then mixing the various quantities of sewage water containing activated sludge in an analysis fermentor and measuring the biological oxygen of the fermentors. This demand is then recorded and the measurements converted to control signals to control the recycling of activated sludge of the plant.
U.S. Pat. No. 4,329,232 discloses a process for rapidly determining the viable organism content in a wastewater treatment system. The test procedure involves aerating a suspension of biomass to be tested until the dissolved oxygen content reaches about 6 mg oxygen/liter and then determining an Oxygen Uptake Rate (OUR) as a function of time. This Oxygen Uptake Rate is then compared to another Oxygen Uptake Rate for a biomass sample which has been aerated and suspended in a standard substrate as above.
U.S. Pat. No. 3,635,564 discloses a quantitative measurement for determining the organic material contained in an aqueous solution and primarily for determining the effectiveness of a wastewater treatment process. The analysis technique described required the measurement of the refractive index and electrical conductivity of the water test sample in relation to the refractive index and electrical conductivity of a known solution. The difference between the refractive index and electrical conductivity of the unknown sample is correlated with respect to known systems containing various organic content. Earlier processes used COD and BOD analysis which requires a substantial amount of time.
U.S. Pat. No. 3,567,391 discloses a method for analyzing the biological oxygen demand in wastewater, and the process involved the use of a pyrolsis chamber functionally connected to a hydrogen flame ionization dectector. Like U.S. Pat. No. 3,635,564 and many prior art processes, this process involved the direct measure of respiratory oxygen requirement of bacteria in the sample.
U.S. Pat. No. 3,510,407 discloses a method for determining the amount of oxygen that will be consumed in the stabilization of organic material in a biological treatment system. The process involves measuring the rate of oxygen consumption at successive times until the rate of oxygen consumption assumes a substantially steady state, that state which is representative of auto-oxidation. The Oxygen Uptake Rate is then integrated as a function of time.
U.S. Pat. No. 3,224,837 discloses various prior art techniques for the determination of organic substances in water utilizing the measure of biological oxygen demand by a bacterial culture and acknowledged these methods were troublesome and time consuming. An electrolytic process is shown wherein organic impurities in the aqueous medium are oxidized to carbon dioxide and the carbon dioxide content measured. The carbon dioxide content is then correlated to organic content.
U.S. Pat. No. 3,731,522 discloses that it was common practice to measure oxygen consumption rate in sewage by activated sludge in order to determine the rate of bacterial growth. The patentees noted the five-day biological demand test as one of the most common and acknowledged that this analytic technique was unduly time consuming and did not provide sufficiently rapid results to enable alteration of processing of the sewage.
To summarize, the prior art has utilized a variety of processes to determine the quality of sewage and its effect on a biological treatment system. Processes which have relied on the use of biological testing of the sewage typically have been inaccurate, not reproducible, and time consuming. Other tests which may have been quicker to run and more reliable in determining quantitative organic content, etc., often do not reflect the impact the particular organic will have on the microorganisms.